Pebax® 1041 supported membranes with carbon nanotubes prepared via phase inversion for CO₂/N₂ separation

This work shows the preparation of Pebax® 1041 films from solutions in DMAc and water-DMAc emulsions as alternatives to those prepared by extrusion that can be found in the literature. These membranes were tested in post-combustion CO2 capture, in the separation of a 15/85 (v/v) CO2/N2 mixture. Self-supported membranes of Pebax® 1041 were prepared by solvent evaporation and phase inversion. The characterization of these films defined the intrinsic properties of this polymer in terms of chemical structure, crystallinity, thermal stability and gas separation performance (a CO2 permeability of 30 Barrer with a CO2/N2 selectivity of 21 at 35 °C and 3 bar feed pressure). Supported Pebax® 1041 membranes were also developed to decrease the Pebax® thickness (in the 1.5-10 μm range), resulting in a higher permeance. These membranes were prepared by a phase inversion process consisting of the precipitation of a Pebax® 1041/DMAc solution in water and dispersing it to form a stable emulsion that was drop-cast on PSF asymmetric supports. Once dried, the polymer formed a dense continuous layer. The phase inversion methodology is "greener" than solvent evaporation since dimethylacetamide is not released as toxic vapour during membrane preparation. The amount drop-cast led to a different selective layer thickness, which was enhanced by the dispersion of MWCNTs in the polymer emulsion. The properties of the Pebax® selective layer were studied by thermogravimetry and by measuring the contact angle of the membrane surface, and the optimal CO2/N2 selectivity (22.6) was obtained with a CO2 permeance of 3.0 GPU.